This project has as its goal a determination of the mechanism by which electronic excitation can be degraded in large organic molecules and molecular complexes. Among the specific projects under study are investigations of the photoreactions of metalloporphyrins in solution and in organized monolayer assemblies, studies of exciplex formation and reactivity in solution, and spectroscopic and photo chemical studies of olefins, dienes, and polyenes in monolayer assemblies. In the first and last of the aforementioned areas the contrast in behavior between reactions in solution and the semi-rigid organized environment provided by monolayer assemblies is under investigation. Preliminary studies of systems formed by reactive self-organizing surfactant molecules suggests that striking differences may be anticipated. The third area of investigation makes use of molecules exhibiting strong phosphorescence from room temperature solutions as probes to investigate details of exciplex formation and energy transfer quenching processes. BIBLIOGRAPHIC REFERENCES: F.R. Hopf, T.P. O'Brien, W.R. Scheidt and D.G. Whitten, "Structure and Reactivity of Ruthenium(II)Porphyrin Complexes. Photochemical Ligand Ejection and Formation of Ruthenium Porphyrin Dimers," J. Amer. Chem. Soc., 97, 277 (1975); G.L.B. Carlson, F.H. Quina, B.M. Zarnegar and D.G. Whitten, "Excited State Interactions and Decay Routes in Bichromophoric Systems. Nonconjugated Phenyl Ketones," J. Amer. Chem. Soc., 97, 347 (1975).